Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnlyHint, idempotentHint, openWorldHint and non-destructive, so safety is covered. The description adds genuine behavioral context beyond them: sampling happens only on whole minutes Kellian observed, gaps yield no bar, and bars are minute-counted rather than uniformly filled. It omits limits on window length / max bar count, which is the main remaining gap.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Front-loaded with the verb and resource, then the returned fields, then usage and a caveat. Dense but every sentence carries content; the nested parenthetical defining the index is slightly heavier than needed.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

An output schema exists so return values need no explanation, and annotations carry the safety profile. The description covers what a bar is, sparsity, and interval alignment; the missing piece for correct invocation is any bound on window size or result volume.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 75% with from/to and interval already documented (including the 9:30 ET alignment note). The description adds little parameter detail, and notably the un-described `symbol` parameter's `<TICKER>-<QUOTE>` shape is not explained in prose either.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb and resource: read the Kellian Perps index as OHLC bars over a window, with the parenthetical defining the index as the underlying instrument price sampled per minute. It implicitly separates itself from market-price chart siblings (kellian_get_market_chart) by scoping to the index/underlying, though it never names that sibling explicitly.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

"Use it for the real range of a price market's window" gives a positive use context, and "a minute not recorded has no bar" warns about sparsity. But there is no when-not guidance and no named alternative (e.g. market chart vs index bars), so the agent must infer which tool to pick.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.